Ban made the statement on January 29 at a news conference in Kuwait, where representatives of some 60 countries participated in the donors conference.

The United Nations' initial aim was raising pledges of about $1.5 billion to provide aid to an estimated 5 million people affected by Syria's 22-month conflict, and an estimated 700,000 refugees in neighboring countries.

The secretary-general said that "the exact amount of the pledges are being calculated," and added that the Kuwait gathering was "the largest humanitarian conference in the history of the United Nations."

Ban said the UN would ensure the money will be used in the most effective way. He said the international community had sent the Syrian people a message that they "are not alone."

About $1 billion is allocated to Syria's neighbors hosting refugees and $500 million for humanitarian aid to Syrians displaced inside the country.

Ban said the $500 million would be distributed through UN partner agencies in Syria, and the entire aid pledge would cover the next six months.

He also called for immediate UN action to stem the crisis. "I urge again members of the Security Council to feel the sense of responsibility to humanity and history. We cannot go on like this," Ban said.

"What is a more important fact is that primary responsibility rests with the Syrian government and President al-Assad. He should listen to the voices and cries of so many people."

Kuwait's Deputy Foreign Minister Sheikh Sabah Khalid al-Sabah said that "the door is open for countries that have not donated to do so."

The conference opened with a pledge of $300 million from Kuwait, followed by similar promises from Saudi Arabia and the United Arab Emirates. The European Union and the United States had promised a total of nearly $400 million.

Russia and Iran, key allies of Syrian President Bashar al-Assad, also attended the Kuwait conference.

Israeli Strike

Meanwhile, Syria's opposition chief on January 29 said he was ready for talks with Assad's regime, subject to conditions.

Syrian National Coalition leader Moaz al-Khatib's surprise announcement came after UN envoy Lakhdar Brahimi said the war had reached "unprecedented levels of horror."

And amid concerns that Syria's stockpile of chemical weapons could fall into the hands of Lebanon's Shi'ite militia Hizballah, Israeli forces carried out an air strike on a convoy near the Syria-Lebanese border.

Western diplomats and regional security sources said the reported attack occurred overnight.

It was not immediately clear what the convoy was carrying, what forces carried out the attack, and whether it took place on the Syrian or the Lebanese side of the border.

Israel has in recent days repeatedly warned of the threat of weapons from Syria, including chemical weapons, falling into the hands of Hizballah.

Israeli officials have said that would likely trigger Israeli intervention.

Israel fought a war in Lebanon against Hizballah in 2006.

Syria and Israel are technically at war after a cease-fire ended their last armed conflict in 1973.